As with previous hostile bids, Roche has upped its offer for Illumina to $6.7 billion or $51 a share.

NEW YORK ( TheStreet) -- After extending a $5.7 billion January hostile bid for Illumina ( ILMN) multiple times in March, Roche has upped its bid for the genomics machinery company by 15% to $6.7 billion -- or $51 a share -- as many investors and analysts expected.

The proposal by Roche is its third hostile bid in the U.S. pharmaceuticals sector after taking a previous $46.8 billion offer for Genentech and a $3 billion bid for Ventana Medical Systems directly to shareholders. With Thursday's offer price increase, Roche has come back to the table with a higher bid in all three instances.

Still, Roche may need to add to its amended offer for Illumina.

"While we were expecting a raised offer, we were not expecting a raised bid so soon after the initial bid. We still anticipate a higher bid, potentially mid-year, to take advantage of anticipated weakness in the space surrounding 2013 National Institute of Health funding," wrote Mizuho Securities analyst Peter Lawson in a note reacting to the bid. Lawson gives Illumina shares a price target of $62.

"We view today's move as the next step, rather than the final step, in the process that we still ultimately believe will lead to a deal... The important question is whether or not the increased bid is enough to bring Illumina to the negotiating table and allow Roche to learn more about Illumina's closely guarded pipeline," noted JPMorgan analyst Tycho W. Peterson, who rated shares "overweight" with a $70 a share price target. Analysts give Illumina an average price target of $55.38, according to consensus estimates polled by Bloomberg.

For investors betting on a bid increase, Roche's new $51 a share offer price represents a relief, as the bid came up against multiple deadlines and Illumina enacted a "poison pill," which could have led to Roche's withdrawal. Investors will have until April 20 to tender their shares, Roche said in a Thursday statement. Separately, Illumina said that shareholders should take no action until the company's board reviews the bid and makes a recommendation.

When Roche first announced the offer on Jan. 25, Illumina shares rocketed past the $44.50 initial price to levels over $55 a share. However, as the takeover attempt dragged on, Illumina shares fell below $50 as some lost their confidence that a higher offer would emerge.

In afternoon trading, Illumina shares were up over 4% to $52.05. Year-to-date, Illumina shares are up over 60%, fueled by Roche's takeover interest, more optimism on the market for its genetic sequencing machinery and speculation that other drug giants could bid on the San Diego-based company.

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In a Thursday statement, Roche Chief Executive Severin Schwan said that the company increased its bid as a way to expedite the merger and help with negotiations, which appeared stalled earlier in March. "Based on our discussions with Illumina shareholders we have seen interest to accelerate the takeover process," said Schwan.

Analysts had called the January bid "opportunistic" and "undervalued," with many pointing to a higher eventual bid by Roche or a competing offer by healthcare giants like Siemens Healthcare ( SIE) and Johnson & Johnson ( JNJ), Abbott Laboratories ( ABT) and Becton, Dickinson ( BDX).

Risk arbitrage analysts at Makor said that the move was a first step to an eventual $55 a share takeover. In April, Illumina's annual shareholder meeting and Roche's now upped offer price will likely move the bid forward. Roche recently appointed a hostile slate of directors to Illumina's board. "These elections will clearly favor the bid from Roche," wrote Makor analysts, who expect a deal completion by mid-June.